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"the ‘system .and .its :strict .torus form; :shear .in the :wind, -both horfzontal .and : vertical,
will deform and ultimately :destroy .the :circulation. , :However. during .the .early .stages of
‘cloud formation, there :is :surptlsingly little deformation, ‘especially :with :the .larger .de‘fonations. ,.
—“~e
1. -The ‘stem should . bhecsndi :effect, ‘that :is, It will .be located :in .approxi-
mately .the .position of the .oxial :streamline :that .ends .at the ground .and passes .through
:the center of ‘the ring.. ‘Radiooctive material, naturally, .can .be ‘carried :into :it as .a
result of the :citcuitous motion .of ‘the -bomb ‘material .around .the vortex ring during :its
ascent; there will .also be .some fall-out of .farger particles. ‘However, “if the explosion
‘Is .sufficiently high :in ‘the .atmosphere, the visible .stem .material, when Lit is ‘stirred up
from :the .ground and not the result.of condensation :in.a aoist atmosphere, may not .reach
‘the central portions of the ring.
Qn the other hand, with some low level detonations, the
stem may pass completely ‘through the ring ond .be visible as .a plume protruding through
it.
.In a moist otmosphere, as ‘in the Marshall :Islands, these oppearonces are .not to
be expected, -since condensation will occur on .all ‘trajecforfes thaf pass :upward through
‘the condensation level. :The stem :in these ‘cases will ‘consist portly of bomb material,
portly of surface material, but largely of ‘condensed ‘water.
With very large bombs, where
-turbulence cannot have any .immediate .large:scale effect on ‘the .form of the .sfem, this
‘structure should consist of smooth laminations corresponding to the differences ‘in ‘wafer
-vapor distribution along the .vertical :in the environment.
:The stems of :large bombs
should appear different in structure from those of smalf ones.
2.
The stems should in mony cases show spiral markings, especially in their
lower portions.
This is due to the convergence ‘induced in :the lower atmosphere by
the ‘vertical circulations. ~The direction of rotation of the spiral will depend on .the
-sign of the vertical component of ‘vorticity in the lower atmosphere: if the horizontal
wind shear at the time of explosion is cyclonic, the ‘stem should show a twist in the
positive sense (cyclonic as seen from above); the opposite ‘circulation should be observed under anticcyclonic ‘shear ‘conditions.
assumptions.
“This deduction :is based on simplifying
First, Coriolis’ force has been neglected; if the horizontal winds set up
after the explosion are large in magnitude as they probably .cre, the effect will be to
produce only cyclonic twists ‘in the stem, the anticcyclonic being damped | Second, the
horizontal ‘variation .in vertical velocity .and the :vertical shear in the winds have been
‘neglected; these, if large. could produce complicated rotations :in the stem which, without empirical data it is not possible to evaluate. |
3.
During ascent of the vortex ring -air should be moving some distance ahead
of the ring (see Figure 3).. The effect of this movement should somztimes be visible,
more especially if a stuble moist layer lies .in the higher atmosphere.
:Then .c cap
cloud similar to the pileus seen on many tropical cumulus, should be visible close to
but moving: aheod of .the vortex ring. |
Pe
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